Although the negative impact of posttraumatic stress disorder (PTSD) on psychological distress is broadly consistent across the literature, the psychological mechanisms underpinning this relationship need further exploration. Pain paradox theory has postulated the important role of PTSD, avoidance strategies, mindfulness, and distress following trauma. However, a more comprehensive study is needed to understand their interactive effects over time. This current longitudinal study aimed to examine the associations between these factors. 201 participants completed the questionnaire survey (i.e., the PTSD Checklist for DSM-5, Toronto Alexithymia Scale, Mindfulness Attention Awareness Scale, and the General Health Questionnaire) at two time points nine months apart. An autoregressive cross-lagged panel with structural equation modelling was used for data analysis. Initial PTSD symptoms predicted subsequent psychological distress. Initial mindfulness was significantly negatively correlated with subsequent alexithymia, PTSD, and distress outcomes. Furthermore, initial alexithymia was significantly positively associated with subsequent PTSD and distress. Following trauma exposure, individuals may develop PTSD that impairs mental health. However, individuals with higher levels of mindfulness tend to experience less alexithymia and PTSD symptoms, which in turn may lead to lower levels of psychological distress over time. Meanwhile, individuals with lower levels of difficulty identifying and describing emotions are less likely to develop PTSD symptoms and experience psychological distress over time.